The present invention comprises a new and distinct cultivar of Rhododendron hybrid used as a rootstock known by the varietal name ‘Rhodunter 37’. The new variety was discovered in Ahrensburg, Germany. The new variety is the result of a planned breeding program between an unpatented Rhododendron fortunei (female parent)×cv. ‘Cunningham's White’ (unpatented male parent). The new variety exhibits matroclinal morphological features. ‘Rhodunter 37’ exhibits more prominent leaf venation than both parents, but is similar in leaf color and shape to both parents. The new variety has been trial and field tested and has been found to retain its distinctive characteristics and remain true to type through successive propagations.